S-35399A02 Datasheet, PDF (46/55 Pages) Seiko Instruments Inc – 2-WIRE REAL-TIME CLOCK

2-WIRE REAL-TIME CLOCK
S-35399A02
Rev.1.0_00
2. Measurement of oscillation frequency
When the S-35399A02 is turned on, the internal power-on detector operates and a signal of 1 Hz is output from the INT1
pin to select the crystal oscillator and optimize the C_g value. Turn the power on and measure the signal with a frequency
counter following the circuit configuration shown in Figure 62.
If 1 Hz signal is not output, the power-on detector does not operate normally. Turn off the power and then turn it on
again. For how to apply power, refer to “„ Power-on Detector and Register Status”.
Remark If the error range is ±1 ppm in relation to 1 Hz, the time is shifted by approximately 2.6 seconds per month
(calculated using the following expression).
10^–6 (1 ppm) × 60 seconds × 60 minutes × 24 hours × 30 days = 2.592 seconds
1 kΩ 1 kΩ
Open
Open
Open
Open
or pull-up
VDD
VDDL
SDA
SCL
CTRL
F32K
FOUT
INT2
S-35399A02
XIN
XOUT
INT1
VSS
Cg ^{10 kΩ}
Frequency
counter
Figure 62 Configuration of Oscillation Frequency Measurement Circuit
Caution
1. Use a high-accuracy frequency counter of 7 digits or more.
2. Measure the oscillation frequency under the use operation conditions.
3. Since the 1 Hz signal continues to be output, initialization must be executed during normal
operation.
46
Seiko Instruments Inc.